The Adult Leukemia Research Center is engaged in a multi-faceted research program with major emphasis on marrow transplantation and ensuing complications. Since its opening in 1969, 113 marrow transplantations have been performed involving allogeneic or syngeneic transplants for the treatment of hematologic malignancies or restoration of marrow function in aplastic anemia. The long-term survival of some of these patients has led to intensification of studies aimed at overcoming some of the problems associated with marrow transplantation. Studies include: role of ultra-isolation and gut sterilization in prevention of infections; efforts to prevent or ameliorate graft-versus- host disease by use of antithymocyte globulin and various immunosuppressive drug regimens; and support of the pancytopenic patient with granulocyte and platelet infusions using the NCI-IBM blood cell separator or the Leuko-Pak technique. Other studies are directed at elucidating the role of prior sensitization by blood transfusion and overcoming this hazard. Chemoimmunotherapy to achieve more effective eradication of malignant cell lines is also under study. Ancillary programs involve cytogenetic studies for confirmation of engraftment, investigation of the role of HL-A antigens in platelet transfusions, and high-dose chemotherapy and autologous marrow storage programs for a variety of malignant diseases.